1. Field of the Invention
This invention relates to a method for making icing. In particular, this invention relates to a method for making icing on an industrial scale which uses a mixing machine having a plurality of independently controlled temperature zones.
2. Description of the Prior Art
Methods for making confectionery cream substances such as chocolate, frosting, icing, and fudges are well known in the art. Chocolates can be made by using a cylinder-like machine that forces a sugary mass through a series of cooling stages. Each stage usually contains blades revolving about an axis. The blades continuously scrape the chocolate mass from the cooling surfaces of the mixing machine. These chocolate mixing machines are designed to condition the chocolate mass by homogenizing and cooling the chocolate mass to an acceptable state for further processing.
Similar conditioning is required for producing an icing, but a chocolate mixing machine is not considered suitable for producing icing. An icing slurry is more abrasive than a chocolate mass and rapidly deteriorates the blades of chocolate mixing machines. An icing slurry also has a higher viscosity than a chocolate mass. The viscosity of an icing slurry requires a more powerful motor to turn the blades of an icing mixing machine than is required for a chocolate mixing machine in processing a chocolate mass.
Icing mixing machines used for making icing on an industrial scale for sandwich cookies or pastry filling usually have mixing chambers surrounded by an externally cooled cylinder. The external cooling of the cylinder is provided by pumping a chilled fluid such as a fluorinated hydrocarbon or water through a jacket placed about the cylinder. Within the mixing chamber of the cylinder, blades are mounted on a rotor which is driven by a motor. In operation the icing slurry is pumped into the entrance of the icing mixing machine. The rotation of the blades mixes and propels the icing slurry through the cylinder. The icing is also aerated and cooled as it passes through the cylinder of the icing mixing machine. The cooling of the icing slurry is regulated within the cylinder by monitoring the exit temperature of the icing. If the exit temperature of the icing is too high or too low for proper crystaline formation, the input temperature of the chilled fluid to the cooling jacket of the cylinder is appropriately adjusted to obtain the desired exit temperature for the icing. Icing mixing machines, according to this description, are sold under the name Votator by the Anco Votator Division, Cherry Burrell Corporation, Louisville, Ky. Votator machines do not permit the temperature within the mixing cylinder to be controlled in distinct stages as the icing is being formed. Without distinct multiple stages of control of the temperature within the cylinder, variations in the crystallization and the specific gravity of the icing occur as the icing is being formed. These variations respectively cause changes in the quality or "mouth feel" of the icing and the amount of icing which must be applied to a food product to obtain a specified weight.
Variations of the specific gravity of an icing determine the "tolerance" at which the icing can be injected onto food stuffs. If the variation in the specific gravity of an icing is significant, more icing must be applied to each cookie or pastry to ensure that those cookies or pastries, which receive icing with a low specific gravity, receive a sufficient volume of icing to meet a minimum weight standard. A significant variation in specific gravity is generally .+-.0.05 or more in the icing being produced. An icing mixing machine that can produce an icing at a consistent specific gravity decreases the tolerance or amount of overfilling of icing onto food stuffs. With a decreased variation in the weight per unit volume of icing produced, less food stuffs are overfilled. When less overfilling of food stuffs is required, a significant economic benefit can be realized by a commercial scale bakery.
Fat crystals that are formed in an icing exist in a number of separate and distinct crystalline phases. The designation of these crystalline structures are alpha crystals, beta prime crystals, intermediate crystals, and beta crystals. The alpha crystalline structure is the least stable crystalline phase. These crystals are loosely packed and do not lend themselves to aeration. The intermediate and beta crystals are more stable during aeration than alpha or beta prime crystals. This additional stability is due to the closely packed structure of these crystals. These crystals are comparatively large and entrap larger air bubbles than the alpha or beta prime crystals. By entrapping larger air bubbles, a less stable icing is produced which results in a product having poor storage characteristics.
The desired crystalline structure to be obtained in an icing is the beta prime crystalline structure. The beta prime crystalline structure of a fat enhances the aeration qualities of the icing being produced. Beta prime fat crystals have a small size of approximately 1 micron which results in a crystal lattice structure that enables large quantities of very small air bubbles to be entrapped in the icing. A large amount of very small air bubbles in an icing produces a product having a very desirable mouth feel. The beta prime fat crystalline structure can be produced in an icing by carefully controlling the cooling of an icing as it is being mixed and aerated.
U.S. Pat. No. 3,914,453 to Gawrilow discloses a process for preparing bakery products. This patent uses a multi-purpose shortening to produce a variety of baked products including fillings. This patent discusses the importance of beta prime crystal structures for fats used in bakery goods. This patent does not disclose a method for making an icing with a consistent specific gravity.
U.S. Pat. No. 2,677,942 to Schott et al. discloses a cooling machine for oleaginous substances. This machine has chambers wherein scrapers mix the oleaginous substance and pass it through the apparatus. Between each scraper are thin walled containers which hold a cooling medium or fluid. The flow rate of the oleaginous composition through the machine is controlled. This machine provides a large cooling surface for contact with the oleaginous substances as it is being mixed. This machine does not have controlled temperature zones between each stage.
U.S. Pat. No. 4,059,047 to Sollich discloses a conditioning machine for chocolate masses. This machine also has blades or scrapers which mix and propel the chocolate mass through the apparatus. These scrapers are in chambers separated by cooling surfaces. This apparatus provides a large cooling surface for the chocolate mass as it is passed through the machine. The cooling zones cannot be individually controlled.
U.S. Pat. No. 2,507,477 to MacDonald et al. discloses a system for preparing a confectionery cream. This apparatus moves a cream through a cylindrical chamber with blades or paddles. There are no individually controlled cooling elements between these blades or paddles. The cooling in this apparatus is provided by pumping a chilled liquid through the external wall of the chamber.
U.S. Pat. No. 3,962,473 to Lilov discloses a staged cooling apparatus for making crust liqueurs for chocolates. The liqueurs which are cooled pass through a drum that has an external cooling jacket. Within the drum is a rotatable shaft on which scrapers are mounted. Controlled multi-stage cooling can be achieved by operating a number of these devices connected in a series by tubes. This method does not use an apparatus having a single cylinder containing all the mixing blades and cooling plates.
U.S. Pat. No. 4,104,412 to Fischer et al. discloses a system for making aerated candy. A candy composition passes through an apparatus that has a rotor with arms that are rotated in chambers. Controlled multi-stage cooling of the candy composition is not achieved with this apparatus.
The industry is lacking a method for making icing that provides controlled multi-stage cooling of an icing slurry as the slurry is mixed and aerated. The method of this invention makes an icing by employing an apparatus that provides a controlled temperature reduction of an icing slurry in stages. This process enhances the formation of desirable small beta prime fat crystals in a high sugar icing composition. This controlled crystal formation allows the icing to "set-up" or solidify rapidly. An abundance of small beta-prime crystals enables the icing to entrap air bubbles and produce a desirable mouth feel. The controlled multi-stage cooling of the method of this invention provides continuous production of an icing having a consistent specific gravity.